European space scientists will this week embark on one of the most daring operations ever undertaken in interplanetary flight. Wednesday they will their Jupiter Icy Moons Explorer (Juice) to make a flyby of Earth and its moon and perform the first dual-gravity-assist maneuver in space.
The delicate, high-risk exercise is essential to the success of the European Space Agency (Esa) mission and aims to take the €1.6bn (£1.4bn) rover to its target, Jupiter, by July 2031. There, it will begin exploring two of the giant planet’s moons, Europa and Ganymede, in an attempt to find signs of life that may lurk in their ice-covered oceans.
However, the maneuver will require exceptionally accurate navigation. The slightest mistake could throw Juice off course and doom the mission, Esa warned. “It’s like going through a very narrow corridor, very, very fast: pushing the accelerator to the maximum when the margin on the side of the road is only millimeters,” said Juice’s spacecraft operations manager, Ignacio Tanco, said.
The craft’s delicate celestial dance will begin Wednesday when it passes near the moon and then flies toward Earth, exploiting their gravitational fields to change its speed and direction as it sweeps across the two worlds and into the inner solar system in a pendulum motion. A flyby of Venus will then take place next year, followed by two further flybys of Earth in 2026 and 2029 before Juice finally departs for Jupiter.
It’s an extraordinary interplanetary waltz that will require Juice to travel at exactly the right speed, time and direction for each encounter. However, without such precise maneuvers, space engineers simply could not explore the Sun’s more distant planets, says Esa.
Flying straight to Jupiter would require Juice to carry 60,000 kg of propellant, an infeasible load. Additionally, it will need more fuel to slow down so it can enter orbit around the planet. That means the scenic route, which uses the inner planets to get gravitational help to reach its target, is the only way to get to the outer solar system, scientists say.
This is an approach that will also be adopted by Nasa later this year when it launches its own Jovian moon mission, Europa Clipper. Its trajectory will sweep the probe over Mars and then return to Earth for a second flyby to increase its velocity. Although it launched more than a year after Juice, it will reach Jupiter in 2030 and will focus its attention on Europa while making its European counterpart Ganymede its main target.
“We know Europa has an ocean under the ice on its surface and we’re pretty sure Ganymede has one too,” said Prof Emma Bunce, director of the Institute for Space at Leicester University. “This makes them extremely interesting targets for our attention.”
Juice and the Europa Clipper should both make important contributions to the search for life in our solar system and that means a lot depends on how well Esa and Nasa space engineers deal with their flyby encounters – starting with Juice’s maneuvers this week.
“It’s going to be very exciting and a little hairy,” Bunce added. “Nevertheless, this maneuver is going to be essential to the mission. The more precisely this is carried out, the less fuel we will need to make future course corrections and we will have more to use to explore Jupiter and its moons.”
Bunce, who was closely involved in the construction of two of the instruments fitted to Juice, added that the probe was not designed to directly detect life on Jupiter’s moons. “It’s going to address the question of habitability by studying the properties of the subsurface oceans. This will tell us if life can be present or not. Actually sense that life will be much more difficult.”
The idea that we could find alien life on ice-covered moons around planets in deep space would have seemed ridiculous a few decades ago. It was assumed that planets closer to the Sun, especially Venus and Mars, offered the best hope.
But Venus has been found to have a surface temperature of 475C, while its atmosphere has a crushing, unbearable pressure that has pulverized robotic probes that land there. In addition, it was discovered that Mars lost its atmosphere and surface water billions of years ago. Efforts to find evidence of life below the surface have so far yielded no results.
In contrast, probes launched several decades ago revealed that three of Jupiter’s main moons – Ganymede, Callisto and Europa – are worlds of ice covered with vast oceans of liquid water, the one prerequisite for the existence of life on Earth. “If there was ever a next best place to look for life, it’s here,” says American astronomer Neil deGrasse Tyson.
The problem is that they are very difficult to achieve. Trips to Mars take about eight months. Juice – launched last year from Esa’s spaceport in Kourou, French Guiana – will take eight years to reach its target as of this week, thanks to all the planetary flybys it will require.
